What is the best way to identify the data type of elements in an array using TypeScript?

When working with TypeScript, it is common to reference interface properties using syntax like Person['gender']. This allows for clear definition of types in TypeScript, as shown in the following example:

interface Person {
  gender: 'male' | 'female';
  addresses: {
    city: string,
    street: string
  }[];
}

let person: Person = {
  gender: 'male',
  addresses: [],
};

let gender: Person['gender'] = person.gender;

Can we also retrieve the array item type of Person['addresses'] in a similar manner?

Note: While creating an Address interface may seem more appropriate in some cases, referencing types this way can sometimes be more concise and easier to follow.

Answer №1

This TypeScript code may seem a bit odd at first glance, but it is indeed valid:

const personAddress: Person['addresses'][0] = {
  city: 'Budapest',
  street: 'Kossuth',
}

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